When water is to be pumped out of an outdoor pit, reservoir, or canal, it is important to prevent debris, such as leaves, sticks, discarded plastic and paper articles, stones, etc., from entering the pump. Rotary self-cleaning strainers that contain cylindrical screens for performing the straining function are often used for this purpose.
The strainer is attached to the end of a conduit and placed in the body of water that is to be pumped. The pump is operated to suck water through the strainer and conduit, as the strainer screen prevents debris from being sucked into the conduit along with the water. Certain debris may adhere to the screen's exterior due to the pump suction force. However, the continued adherence of such debris to the screen's exterior, and resulting impairment of flow through the screen, are prevented by rotating the screen past a nozzle structure which is disposed on the interior of the screen and directs water outwardly through the screen to dislodge the debris. The water is fed under pressure to the strainer through a separate supply line which may be tapped into the pump's outlet. The water acts on only a limited circumferential zone of the screen at any given time to force adhering debris away from the exterior of the screen as the screen revolves past the nozzle structure. The remainder of the screen serves to pass the flow of water that is being sucked by the pump.
Commonly assigned U.S. Pat. Nos. 4,822,486 and 5,108,592 disclose new and improved rotary self-cleaning strainers of this general type. One feature of these strainers is the use of nozzles directed to eject pressurized water against the cylindrical screen to rotate the rotary portion of the strainer and simultaneously dislodge adhering debris from the exterior of the screen. Further improvements are the subject of commonly assigned U.S. Pat. No. 5,356,532.
Annular end closure discs close the opposite axial ends of a rotary portion of the strainer to the non-rotating central core of the strainer. The core comprises a suction pipe through which water from the source being pumped is sucked out of the strainer, and a supply pipe that extends coaxially within the suction pipe to deliver pressurized water to the nozzles that are disposed at the radially outer ends of pipes which are threaded into the wall of the supply pipe. These end closure discs are rigid plastic. An axial end of the rotary portion may be closed to the suction pipe by either a single disc, or by a stack of plural discs. Mounted on these annular end closure discs are means providing for the journaling of the rotary portion on the non-rotating central core about the strainer's longitudinal axis.
In all three of these referenced patents the journaling of the upper end closure to the suction pipe is provided by a series of identical diameter wheels that are mounted on the lower face of the upper annular end closure to rotate about axes that are parallel with the strainer's longitudinal axis. For example, in the latter referenced patent there are four such wheels at ninety degree intervals around the axis of the strainer, defining an imaginary circle that is concentric with the strainer axis and slightly smaller than the I.D. of the annular end closure such that the wheels just touch the O.D. of the suction pipe. In the first two referenced patents, an annular seal is mounted on and sealed against the upper face of the upper end closure around the margin of its I.D. In radial cross section this seal has a lip that curves into sealing contact with the O.D. of the suction pipe. The lower end closure is journaled on the lower end of the central core, but the journaled surface of the central core is not the O.D. of the suction pipe.
Commercially available PVC pipe is typically used as the suction pipe in the strainers described in the referenced patents. It has been discovered that over the life of a strainer the set of journaling wheels often wears a groove around the outside of the PVC suction pipe. This is attributed to the PVC pipe being less hard than the material of the journal wheels. Such a groove creates looseness in the upper journal, and such looseness may ultimately reach a point that defines the end of the useful life of the strainer even though the depth of the groove is insufficient to significantly impair the strength of the suction pipe.
One aspect of the present invention relates to a novel bearing-seal for the upper journal of a rotary strainer that allows a strainer whose upper journal has become too loose to be reconstructed without the necessity of replacing the suction pipe, even though it has been somewhat grooved. Moreover, the inventive bearing-seal allows the reconstruction of the strainer to be performed by the user, thereby avoiding the need for the user to return the strainer to the factory for reconstruction. The several parts forming the inventive bearing-seal can be shipped from the factory to the user as a reconstruction kit, including instructions for performing the reconstruction. An especially significant advantage of such a kit is that it can be conveniently installed without substantial disassembly of the worn-out strainer.
Use of the inventive bearing-seal is not limited just to reconstruction of a worn-out strainer. It can be used to advantage in a new strainer instead of the set of wheels heretofore used for journaling the upper end of the rotary strainer portion on the suction pipe. Where sealing is also required, the inventive bearing-seal can replace the aforementioned curved lip seal.
An especially surprising attribute of using the inventive upper bearing-seal is that rotational friction is significantly minimized. This means that the strainer can be operated with significantly increased power efficiency. Such improved efficiency offers the potential for effective usage with lower pressure pumps. Since pump pressures available at certain sites where the strainers are used are sometimes limited, the inventive bearing-seal offers the opportunity for usage at such sites, thereby providing more widespread usage for such strainers.
The foregoing features, advantages, and benefits of the invention, along with additional ones, will be seen in the ensuing description and claims which are accompanied by drawings. The drawings disclose a presently preferred embodiment of the invention according to the best mode contemplated at this time for carrying out the invention.